Endocrine Abstracts

Osteoprotegerin (OPG) is a potent inhibitor of osteoclastic bone resorption. Besides osteoblasts, OPG is expressed by both endothelial and vascular smooth muscle cells. Moreover, elevated serum OPG has been found in conditions associated with insulin resistance such as obesity, diabetes and/or Cushing syndrome.

The aim of the present study was to investigate the relationship between serum OPG and insulin resistance in women with polycystic ovary syndrome (PCOS). In a cohort of 39 women (age 25.3±4.6 years, BMI 25.96±5.34 kg/m²) PCOS was diagnosed according to Rotterdam criteria. After signing informed consent approved by the local Ethical Committee, blood pressure, steroid hormones, gonadotropins, SHBG, blood glucose, insulin and lipid spectrum were determined in fasting state and homeostasis model assessment for insulin resistance (HOMA-IR) was calculated. In addition, insulin sensitivity was determined as glucose disposal in euglycemic hyperinsulinaemic clamp.

Mean serum levels of OPG were 6.33±1.32 pmol/l. In Spearman analysis, circulating OPG significantly correlated with total cholesterol (r=0.35, P≤0.03). In partial correlations, OPG was positively related to age (r=0.46, P≤0.01), total cholesterol (r=0.49, P≤0.01) and FSH (r=0.48, P≤0.007), whereas negative correlations were found between serum OPG and diastolic blood pressure, HOMA-IR and/or HDL cholesterol (r=−0.5, P≤0.005, r=−0.46, P≤0.01 and r=−0.45, P≤0.012 respectively). There was no significant relationship between glucose disposal and serum OPG levels.

In the present cohort of women with PCOS, serum OPG levels were significantly associated with diastolic blood pressure, insulin resistance assessed by HOMA-IR and an adverse lipid profile. A possible contribution of OPG to insulin resistance and vascular endothelial dysfunction in PCOS needs to be further investigated.